Artificial shoulder-forming retaining rings designed to self-lock themselves solely by friction to the external surfaces of (grooveless) carrier members such as shafts, especially small-diameter shafts, spindles, rods, pins, etc., are well known, having been disclosed and claimed in U.S. Patent to Heimann U.S. Pat. No. 2,574,034 dated Nov. 16, 1951. According to said patent, rings of this type are calculated so that their maximum section height will provide maximum gripping pressure uniformaly all around their inner edges when spread within their elastic limit to the diameter of the shaft and assembled thereon.
Since the thrust resistance capable of being provided by said rings with respect to machine parts to be located or positioned thereby is equal to the aforementioned gripping pressure times the friction coefficient of the inner circumferential ring-edge with the surface of the shaft, it becomes obvious that in shaft-ring combinations constructed according to the prior designs the outer dimensions of the self-locking rings are limited by the distance of the shaft surface from the outer edge of the ring at the point of its maximum section height. Such a limitation becomes extremely critical in the case of small shafts of 1/16 inch diameter and even less. Further, because of manufacturing tolerances, continuing experience with rings of such small sizes constructed according to the patened design has shown that their performance is somewhat irregular and to a degree unreliable. Additionally, the production of such small rings according to the known self-locking design has been proven to be very expensive.